of worcester



- March 17, 1925.

J. A. OLDSON BALANCED CRANK SHAFT riginal Filed Je n. 8, 1923 o [fie/ Zion Reissued Mar. 17, 1925.

UNITED STATES PATENT OFFICE.

JOHN A. oLnsoN, or woncnsrrm, massnciiusn'r'rs, ASSIGNOR 'ro WYMAN-GOBDON comm, or woncnsrna, MASSACHUSETTS, A conroaarron or MAssAcnUsET s,

BALANCED CRANK SHAFT.

' Orlglnal 80. 1,512,479, dated October 21, 1924, Serial No. 611,237, filed January 8, 1928. Application for reissue filed January 20, 1925. serial No. 3,703.

' ceedingly simple construction for balancing a multiple crank shaft, by means of which the running qualities of the shafts are much im roved. In such shafts, unbalanced centri ugal forces are developed by the different cheeks, which produce an increasing tendas the speed increases.

Many methods of counter-balancing such shafts have been developed, commonly by separately counter-balancing each separate check by bolting or otherwise securing a counter-Wei ht thereto. This procedure involves muc labor and greatly increases the wei ht and cost of the shaft.

It is 51c object of my invention to provide a much simpler and cheaper construction by means of which all necessary counter-balancing effect may be obtainedand a highl efficient and satisfactoryshaft may be pro uced.

With this general object in view, my in vention consists primarily in providing a single counter-weight for each pair of adjacent checks in a crank shaft, so proportioned and disposed that it will effectively counter-balance the resultant of the unbalanced centrifugal forces of two adjacent crank-shaft cheeks.

In the drawings, my invention is shown embodied in a six-throw three-bearing shaft, having the usual straight single cheeks adjacent the shaftbearings and having intermediate curved cheeks connecting adjacent crank pins. As applied to a shaft, of this type, each counter weight counter-balancesone straight or single cheek between a crank in and a crank bearing and the next ad acent curved or connecting cheek between two crank pins. Four such counter-weights effectively counter-balance the whole shaft and these counter weights are disposed in diametrically opposed positions, so that they also balance each other and the shaft remains in static balance as it would be without the counter-weights.

ency to distortion and whipping of the shaft" My invention further relates to the provislon of such a shaft in which the counter- 85 weights are forged inte ral with the remaining parts of the shaft, and also to certain arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended 00 claims. 7 i

One form of my invention is shown in the drawings, in which- Fig. 1 is'a plan view of a forging for a six-throw three-bearing crank-shaft; Fig. 2 is a similar-view of the finished shaft;

'Figs. 3 to 10 inclusive are transverse sectional views taken along the correspondingly numbered lines in Fig. 1 and separately showing the different crank cheeks; and

Fig. 11 is a sectional end view of the shaft taken along the line 11 ,1l in Fi 1.

Referring to igs. l and 2, I have s own a six-throw three bearing crank-shaft which is in general of a. somewhat common type, the bearings being designated at 20, 21 and 22 and the crank pins bein indicated by the Roman numerals I to A straight cheek 23 connects the; bearing 20 to the crank pin I. Similar straight cheeks 24 and 24; connect the pins III and IV respectively to the bearing 21. A fourth straight check 25 connects the crank pin VI to the bearing 22. A curved cheek 26 connects ,pins I and II; a curved cheek 27 connects cranks II and III; a similar cheek 28 connects crank pins IV and V and a fourth curved cheek 29 connects crank pins V and VI. Disregarding the counter-weights, it will be evident that the straight cheek 23 (Fig. 3) is out of balance and that rotation thereof will produce an unbalanced centrifugal force acting in the direction indicated by the arrow a. Similarly, the adjacent curved check 26 (Fig. 4) is also out of balance androtation thereof will produce an unbalanced centrifugal force 6.

Referring again to Fig; 3, it will be- 1 evident that a force a is necessary to counter-act the unbalanced force a, and another force 6 is necessary to counter-act the unbalanced force I). Instead'of :1 plying counter-weights to the separate cheeks 1 23 and'26, acting in the directions a and b, i

I have found that entirely satisfactory re-' sults may be obtained by applying a single counter-weight 30 in such a position that it will act along the line indicated by the arrow 6, in the direction of the resultant of the forces a. and b. Such a counterweight eifectively ofi sets the unbalanced weight of both the straight cheek 23 and the curved cheek 26 and these parts are so closely adjacent that the application of the entire counter-balancing force in the single counter-weight 30' is found to be entirely satisfactory throughout the range of speeds at which such crank shafts are operated.

The curved cheek 27 and the adjacent straight check 24 are similarly provided with a single counter-weight 31 acting along the line of the arrow at (Fig. 6). The adjacent cheeks 24* and 28 are counter-balanced by a weight 32 acting in the line of the arrow e (Fig. 7) and the adjacent cheeks 29 and 25 are counter-balanced by a weight 33 acting in the direction of the arrow f (Fig. 10).

It will be noted that the directions of the arrows c and d areparallel but reversed and the same is true of the arrows e and f. The counter-weight 30 thus balances the counterweight 31 andthe counter-weight 32 balances the counter-weight 33 so that the shaft remains in static balance as it would be without the counter-weights.

Remarkably improved results have been obtained by the use of this improved counter-balance construction. For example, a shaft similar to Fig. 1 but without counter-weights, when rotated in yieldingly mounted bearings, showed excessive vibra tion at 1600 It. 1. M., while the same shaft, when counter-weighted as indicated in the drawings, was run at 2400 R. P. M. in the same yielding bearin s, almost without perceptible vibration. buch a shaft mounted in the usual rigid engine frame bearings could be driven at perhaps double the latter speed without injurious vibration. A crank shaft thus counter-balanced is accordingly, efficient and satisfactory at all speeds incurred in the operation of the shafts.

While I have described my invention as particularly applied to a six-throw shaft ha"- ing curved connecting cheeks between adjacent crank pins, it will be evident that many of the advantages of my invention may be obtained in crank-shafts other than the particular one described. It will be also obvious that the mass of each counter-weight must be proportioned for the particular design of shaft to be balanced and that this mass may be proportioned to take account also of the crank pins and if desired, of a portion of each engine connecting rod associated therewith.

In the preferred embodiment of my in1' proved shaft, the counter-weights 30, 31, 32

and 33 are forged integral with the remaining parts of the shafts, a suitable method for attaining this result being disclosed in the prior patent to Larcher No. 1,434,215 issued October 31, 1922. j

I do not wish to be limited, however. in all cases to the formation of the counterweights integral with the shaft and it will be evident that other changes and modifications may be made in my invention within the spirit and scope thereof by those skilled in the art. Therefore I do not wish to be limited to the details herein disclosed otherwise thanas set forth in the claims but what I claim is 1. A three-bearing multiple crank-shaft of unitary forged construction and having adjacent single and connecting crank cheeks disposed in pairs at oblique angles to each other, with the two unbalanced centrifugal forces produced by each such pair of adjacent cheeks acting in different directions, and a single counter-weight for each such pair of adjacent cheeks, angularly positioned to counter-act the resultant of these two unbalanced forces, said counter-Weights being formed integral with said single cheeks, and being positioned closely adjacent a crankshaft bearing.

2. A six-throw three-bearing crank-shaft of unitary forged construction and having, in combination, four single cheeks and four connecting cheeks disposed in adjacent pairs, and a single counter-weight for each pair of adjacent cheeks, angularly positioned to counter-act the resultant of the two unbale anced centrifugal forces produced by a single cheek and an adjacent connecting cheek respectix 'ely, said counterweight being integral with the single cheek and being positioned closely adjacent a crankshaft bearmg.

3. A three-bearing multiple crank-shaft of unitary forged construction and having adjacent single'and connecting crank cheeks disposed in pairs at oblique angles to each other, with the unbalanced centrifugal forces produced by and on each'such pair of adjacent cheeks acting in different directions, and a single counter-weight for each such pair of adjacent cheeks, angularly positioned to counterac-t the resultant of these two unbalanced forces, said counter-weights being formed integral with said single cheeks and being positioned closely adjacent a crankshaft bearing.

4. A six-throw three-bearing crank-shaft having, in combination, four single cheeks and four connecting cheeks disposed in adjacent pairs, and a. single counter-weight for each pair of adjacent cheeks, angularly I positioned to counter-act the resultant of the two unbalanced centrifugal forces produced by a single cheek and an adjacent connecting cheek respectively, said counterweights being associated with the single cheeks and each being positioned closely adjacent a crankshaft bearing.

5. A three-bearing multiple crank-shaft having adjacent single and connecting crank cheeks disposed in pairs at oblique angles to each other, with the unbalanced centrifugal forces produced by and on each such pair of adjacent cheeks acting in different direc- 10 tions, and a single counterweight for each such pair of adjacent cheeks, angularly positioned to counter-act the resultant of these two unbalanced forces, said counter-Weights being associated with said single cheeks and each being positioned closely adjacent a 15 crankshaft bearing.

In testimony whereof I have hereunto affixed my signature.

JOHN A. OLDSON. 

